Functionalized polyolefin (FPO) materials have potential usefulness for a number of commercial applications. Polyolefins that are reactive or polar can, for example, provide products for major applications, such as high temperature elastomers resistant to oil, and can also provide structural polyolefins. Polyolefins in the form of oil resistant elastomers could compete with chloroprene and nitrile rubber in oil resistant applications but could offer better high temperature performance and service life than ethylene-propylene diene rubbers at a comparable price. Structural polyolefins could be low cost polymeric materials with improved stiffness, strength and use temperatures that would extend the boundary of polyolefins to structural applications, for example to uses within the automotive area.
Post-polymerization functionalization requires synthesis of precursor olefin copolymers which carry functionalizable “reactive hooks”, such as residual double bonds or aromatic rings. Such “reactive hooks” can then be appropriately functionalized using various chemistries. Functionalizable copolymer precursors which contain reactive hooks in the form of residual double bonds are conveniently produced by incorporating a diene co-monomer into the copolymer precursor. One of the double bonds in the diene comonomer permits co-polymerization of the co-monomer with one or more α-olefins, while the remaining unreacted double bond in each of the pendent co-monomer moieties along the polymer chain is then available for conversion to selected polar groups via a separate process, generally in a different reactor.
This olefin-diene approach allows production of a wide range of products using a single technology. Functionalization of the diene co-monomers within the copolymer precursor permits the introduction of polarity for oil resistance and can also improve the thermal and chemical stability characteristics of the resulting functionalized copolymer materials. Further, the glass transition temperature, Tg, of the resulting functionalized copolymer can be adjusted by both the choice and content of the diene co-monomer.
One type of known functionalization of olefin/diene copolymers involves reaction of the copolymer precursor material with an oxidizing agent to provide an epoxidized material having oxirane groups formed at the sites of the residual double bonds within the copolymer precursor. Further hydrolysis of such epoxidized materials can convert the oxirane groups to diol moieties within the resulting functionalized copolymers.
It is known to epoxidize olefin-diene copolymer materials, such as ethylene/dicyclopentadiene, using peracids such as performic acid or m-chloroperbenzoic acid as an oxidizing agent. Such epoxidation reactions can provide quantitative or near-quantitative conversion of the residual diene co-monomer double bonds into oxirane groups, with the further possibility of converting some or all of such oxirane moieties to diols. Representative prior art disclosing epoxidation and/or hydroxylation of olefin-diene copolymer materials includes Marathe et al: 27 Macromolecules, 1083 (1994); Sarazin et al; 26 Macromol. Rapid Commun, 83 (2005); Song et al; 40 J. Polym. Sci. Polym. Chem., 1484 (2002); Shigenobu et al (Maruzen Petrochemical); Japanese Patent Appln. No. JP2001-031716A; Suziki et al; 72 J. Polym. Sci. Polym. Chem., 103 (1999); and Li et al; 38 Macromolecules, 6767 (2005).
The catalytic functionalization of unsaturated materials is also known. Rhenium-containing catalysts have been used, for example, to epoxidize and/or hydroxylate a variety of non-polymeric alkenes. And there are a few examples in the art of catalytic oxidation being used to introduce epoxy groups into copolymers containing relatively low levels of unsaturation or unsaturation which is primarily found within the copolymer backbone. Representative prior art disclosing rhenium-catalyzed epoxidation and/or hydroxylation of alkene materials includes Herrmann et al; Angew. Chem. Int. Ed. Engl.; 1991, 30, (1638); Herrmann et al (Hoechst AG); U.S. Pat. No. 5,155,247; Issued Oct. 13, 1992; Van Vliet et al; Chem. Commun.; 1999, pp 821-822; and Soldaini; SYNLETT 2004, No. 10, pp 1849-1850.
Epoxidation of copolymers having higher levels of unsaturated co-monomers is, however, more difficult than functionalization of non-polymeric alkenes, either without or with a suitable catalyst. Such functionalizable copolymers with higher levels of diene-derived co-monomers therein have enhanced potential for side reactions and cross-linking which can be brought about by the presence of greater amounts of organic peracids used as epoxidizing agents. Use of a catalyst can eliminate the need for the presence of large amounts of acidic reagents and can permit the use of peroxides as oxidizing agents. However, the presence of a catalyst can also promote cross-linking or side reactions of the diene-derived comonomer-containing copolymer and/or can also potentially degrade the oxidizing agent which is being used along with the catalyst.
Given the actual and potential usefulness of functionalized olefin/diene copolymers, and especially those functionalized by epoxidation, for a variety of commercial applications, it would be desirable to identify new and efficient processes for preparing such epoxidized and/or hydroxylated copolymer materials. According to the present invention, it has now been found that α-olefin/diene copolymers can be effectively functionalized by reaction with an alkyl hydroperoxide in the presence of a catalyst comprising a metal of Group 5 or 6 of the Periodic Table or a compound thereof. The reaction is not radical-initiated and so side reactions, such as cross-linking, that are common with free radical reactions are substantially eliminated. Also the reaction with hydroperoxide generates an alcohol as a by-product, which can readily be removed and recycled or otherwise processed.
Barradas et al. in Braz. J. Chem. Eng., Vol. 15, No. 2, June 1998, disclose catalytic epoxidation of cyclohexene by tert-butyl hydroperoxide in the presence of a catalyst produced by heterogenization of molybdenum species, starting either with Mo(CO)6 or MoO2(acac)2, on the surface of functionalized silica bearing one (Si-Et1) or two (Si-Et2) ethylenediamine ligands.